The impact of aeration rate on the denitrification performance and microbial community characteristics of the HN-AD bacteria-inoculated MBBR system

This study investigated the influence of aeration rates on the denitrification performance and microbial community of heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria-inoculated MBBR systems treating nitrate wastewater. The results demonstrated high removal efficiencies for COD (93.8 %) and TN (86.2 %) at an optimal aeration rate of 1 mL/min, indicating enhanced TN removal with reduced energy consumption. High-throughput sequencing results revealed that Proteobacteria, Bacteroidota, and Chloroflexi were key players in denitrification, with notable genera including Stappia, Thauera, norank_f__A4b, SM1A02, Pseudomonas, and Flavobacteria. HN-AD bacteria Stappia and Thauera played the key denitrification role at 1 mL/min and lower aeration rate was more conducive to the enrichment of Stappia and Thauera. Functional gene analysis further highlighted the importance of narG, narH and narI in denitrification processes. •Effect of aeration rate on HN-AD bacteria-inoculated MBBR was studied.•86.2 % of TN removal was realized at a lower aeration rate of 1 mL/min.•A lower aeration rate facilitated the enrichment of key denitrifying HN-AD.•The abundance of key denitrifying gene narG, narH and narI were the highest at 1 mL/min.